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An Adaptively Covert, High Capacity RF Communications / Control Link

Description:

TECHNOLOGY AREA(S): Electronics 

OBJECTIVE: Exploit the variable RF path loss near 60 GHz to develop and demonstrate an adaptive, covert, high bandwidth, full duplex, jam resistant communications / datalink. 

DESCRIPTION: The radio frequency (RF) transmission near the 60 GHz (V-Band) oxygen absorption line provides a high capacity RF path in which the path loss can be varied approximately 10 dB / km (see ref. 1) by changing the carrier frequency over a relatively small spectral range. This presents the opportunity to develop high bandwidth RF datalinks and/or networks designed to work only within a limited geographical sector as the frequency, transmission power, and antenna pattern are adaptively controlled to insure connectivity and achieve covertness. The 60 GHz path loss due to the absorption by oxygen in the atmosphere has an exponential behavior and provides an additional degree of freedom to control transmission range. This behavior enables the structuring of an operational sector, which exhibits high transfer rates and robust digital connectivity. At ranges beyond, the RF signal level decreases exponentially below minimum detection levels over a relatively short distance to provide covertness. By automatically tuning the transmission frequency in real time using a feedback mechanism, the physical volume of the operational sector can be adjusted to counteract changes in path loss due to movement of communications platforms or atmospheric conditions. By automating a process for selecting appropriate transmission frequency, transmission power, and antenna pattern, one can optimize in real time the datalink conditions necessary to balance the tradeoff between robust connectivity and covertness in the link or network. Such a dynamic datalink based on 60 GHz technology provides a solution to Army and military needs to increase bandwidth availability for short range communications while minimizing its potential exposure to cyber threats by hostile surveillance or jamming. There are a number of research efforts which have focused on short-range, high data rate communications at 60 GHz, relying on the exponentially varying path loss for covertness. However the frequency adaptive path loss has not been exploited for adaptive geographical coverage in the 60 GHz region. Furthermore, the telecommunication industry has invested in the development of electronically steered 60 GHz antenna arrays for indoor datalink application. A successful link will require a highly innovative electronics architecture to use continuous link feedback to control the size and range of the operational sector in real time while minimizing size, weight, power, and cost (SWaP-C). The challenges include the frequency, power, and antenna array control circuitry and the determination of trade-offs between path loss, power, and antenna circuit complexity. Due to the small wavelength associated with the 60 GHz region, small antenna elements can provide high gains on a small physical array footprint. The control problem is further complicated by the inhomogeneous frequency dependence of the path loss as the carrier frequency is adjusted up and down the oxygen absorption line. As an initial demonstration of these concepts, this SBIR topic addresses the development and demonstration of a full duplex communications / control link between two transceivers. This link will exploit the oxygen path loss at 60 GHz for a wireless real time adaptively covert link to replace the control wire of a wire controlled anti-tank missile or for a ground control / communications link to a UAV. Additionally, dynamically controlled RF power, antenna gain, and beam steering solutions shall be addressed for one of the transceivers, while the other transceiver may be limited to frequency agility only (fixed spectral output power and bore-sight fixed antenna pattern). The same technology will have applications as a basis for commercial or military wireless networks (see for example refs. 2-6). The emerging concepts for 5G wireless networks consider a millimeter wave local area network to distribute digital information in localized areas. The military concern with covertness and jam resistance translate to commercial concern for channel interference. The adaptive nature of this link will accommodate changes due to weather and atmospheric conditions. The link envisioned will have potential usage for fixed or mobile networks or for inter-vehicle communications within a swarm of autonomous UAV’s. With the extensive commercial attention (see ref. 6) and with advances in DoD research programs, the component technology needed for the hardware is available and will advance to higher performance and lower cost as industry plans for 5G networks progress. 

PHASE I: Design a two way RF link described above with its general goal to replace the control wire of a wire guided anti-tank missile (see for example refs. 7-8). The line of sight datalink should operate near the 60 GHz atmospheric absorption line for oxygen and with the capability of tuning over the line sufficiently fast to accommodate the changing geometry of the line of sight missile path, with the missile traveling at up to 250 m/s. The link capacity should accommodate at least 5 Gbps. The path length should be variable between 0 - 5 km using frequency, power, and beam pattern agility. It is expected that higher antenna gains (beamwidth of a few degrees) are necessary for longer transmit distances, while low gain patterns (+/-45 degrees) should be achievable at short transmit distances. A bit error rate of 10E-6 should be guaranteed within the operational sector and increase rapidly outside the operational range. The transceiver exhibiting output power and antenna pattern agility in addition to frequency agility shall be located at the missile launcher, while the less expensive transceiver exhibiting frequency agility only is located at the rear end of the missile pointing towards the launcher transceiver. The transceiver unit on the missile should have a form factor of roughly 8 cm X 8 cm X 4 cm. This form factor is a rough goal, not an absolute requirement. Analyze the tradeoffs between transmit power, frequency, and antenna directivity and their adjustability in maintaining an optimum operational sector over the full flight path in various atmospheric conditions (rain or dust). Analyze the effect of required bandwidth of the signal when operating along the asymmetric oxygen absorption line. Develop the software required to support the link. Design a suitable digital modulation technique for such a datalink. 

PHASE II: Develop, demonstrate, and deliver the hardware and circuitry required for the datalink, with the metrics described above and proposed at the end of Phase I. Demonstrate the adaptive operational sector over the flight path by static measurements at different path distances coupled with analysis or simulation that the circuit will support the geometry changes at flight speed of 250 m/s. Demonstrate by simulation the adaptive operational sector under different atmospheric conditions. Analyze the jamming resistance of the link by calculating for different positions along the flight path, the maximum distance for effective jamming from outside the “bubble”. 

PHASE III: Explore additional developmental funding from the OSD RIF program, other DoD programs, or industrial funding from DoD prime contractors to integrate the missile transceiver onto an operational missile and demonstrate under field conditions. Explore the application for an adaptive secure networks for autonomous UAV swarms or for tactical headquarters on the move. Explore modifying the link for applications to commercial 5G wireless systems. Approach commercial wireless companies for development funding and potential partnering. Transition the technology to commercialization for commercial and/or military applications such as secure links for anti-tank missile or UAV control, secure communications in a tactical headquarters or mobile network, low interference communications in a commercial 5G network, or secure military or commercial mobile communications. 

REFERENCES: 

1: http://www.ece.ucdavis.edu/dmrc/files/2014/09/Bruce_wallace_darpa_web.pdf

2:  E. Parhia, C. Cordiero, M. Park, and L. Yang, "IEEE 802.11ad: Defining the Next Generation Multi-Gbps Wi-Fi," IEEE CCNC Proc. 2010. Doi:10.1109/CCNC.2010.5421713.

3:  R. Daniels, J. Murdock, TS Rappaport, and R. Heath, "60 GHz Up Close and Personal," IEEE Microw. Mag. 11, 44 (2010)

4:  JS Vaughan-Nichols, "Gigabit Wi-Fi Is on Its Way," IEEE Computer 43, 11 (2010).

5:  T. Baykas, C.-S. Sum, Z. Lan, J. Wang, MA Rahman, H. Harada, and S. Kato, "IEEE 802.15.3c: The First IEEE Wireless Standard for Data Rates over 1 Gb/s," IEEE Comms. Mag. 114 (July 2011).

6:  TS Rappaport, J. Murdock, and F. Gutierrez, "State of the Art in 60-GHz Integrated Circuits and Systems for Wireless Communications," Proc. IEEE 99, 1390 (2011).

7:  https://en.wikipedia.org/wiki/BGM-71_TOW

8:  http://www.designation-systems.net/dusrm/m-71.html

KEYWORDS: 60 GHz, Covert Wireless Link, Wireless Missile Guidance, Adaptive Covert Wireless Link, 60 GHz LAN 

CONTACT(S): 

Dr. James Harvey 

(703) 696-2533 

james.f.harvey.civ@mail.mil 

Mr. Martin Heimbeck 

(256) 842-2502 

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